A study used cutting-edge technology to identify the gene mutations in both metastatic breast cancer cells and cells from the original cancer that was diagnosed 9 years earlier. The researchers found that most of the cells from the original cancer had five gene mutations that caused the cells to become cancerous. Nine years later, the metastatic cancer had 21 more gene mutations.

The researchers found that some gene mutations were shared by only some of the cancer cells. This means that the cells that make up a cancer are not all the same. Instead, the cancer is made up of related "families" of abnormal cells and each family has its own set of gene mutations. This is probably why many cancers respond to a treatment for a time -- a long time in some cases -- but then stop responding. It's likely that some cancer cell families in the tumor were destroyed by the treatment while other cell families with different genes were able to survive, thrive, and ultimately take over.

The advanced genetic testing done in this study isn't routinely available right now. Still, understanding the gene mutations that cause normal cells to become cancer cells can help doctors understand how cancer happens and how it might be prevented or treated in a more targeted way. Advanced genetic analysis also may some day help doctors choose treatments that are most effective against the gene mutations in a specific cancer.

Stay tuned to Breastcancer.org for more news on research that may offer better ways to prevent, diagnose, and treat breast cancer.